H Liu et al/ Materials Science and Engineering A 525(2009)121-127 Table 1 Painting Stacking Molding Properties of KD SiC fibers. Slurry KD-2 Curing Diameter (um) 14-16 Sic fiber cloths 14-1 Number of filaments(fil/yarn) 1200 2D-SiCf/SiC Pyrolysis Tensile strength(MPa) 800-22001500-1900 Infiltration 2D-SiCmSic Chemical compositions of fiber surface layer Pyc Silcon-based oxide PCS solution for transmission electron microscope(TEm)observation followed Fig. 1. Preparation route of the 2D-SiC/Sic composites JEM-20io ation procedure described by Appiah et al.[18JJEOL JEM-2010 and Philips CM 200 FEG equipped with a Gatan imag- and d) is relatively rough, and some strumae-like structure defects ing filter(GIF) system were used to characterize the interfacial re found. These defects reduce the tensile strength of Sic fibers microstructure and element distributions in the interphase region. [19 such that the tensile strength of KD-2 Sic fibers is about 85% X-ray photoelectron spectroscopy(XPS )analysis was done using a that of KD-1 Sic fibers VG ESCA-LAB MK ll apparatus with al Ko radiation and calibrated Survey XPS spectra recorded from the surface of KD-1 and KD-2 gainst Au 4f 7/2 and Cu 2p3/2 lines. Raman spectra were recorded Sic fibers are shown in Fig 3a. In the spectrum of KD-1 Sic fibers. vith a Raman spectrometer HR 800 ( obin-Yvon Company, France) no Si lines are observed. a single C ls peak at 284.5 ev is detected, in backscattering geometry at 532 nm excitation wavelength. The which is attributed to the C-Cbond in the PyC. In addition, the pI laser beam was focused in air at normal incidence on a small area ence of a weak o1s peak at 532. 5 ev indicates that some oxygen of the fiber surface(ca. 1 um2), and the laser beam power was exists on the Kd-1 SiC fiber, which originate from a contamination 1 mw. Raman spectra were recorded at wavenumbers from 800 by the glue or sample holder. So, it can be concluded that the Pyc is 2000 cm, and the acquisition time was 30s. The phases of KD the main constituent of the surface layer of the KD-1 SiC fiber Con- d KD-2 SiC fibers were characterized by X-ray diffraction(XRD) cerning KD-2 SiC fibers, the Si 2p and Si 2s peaks are all detected. analysis using monochromatic Cu Ka radiation with a D8 ADVANCE In the Si 2p spectrum of KD-2 SiC fibers( Fig. 3b). only a single Si diffractometer(Bruker, Germany ) 2p peak at 103.6ev is detected which is assigned to the si-o bond in silicon-based oxide, and the si 2p peak cannot be fitted into sub 3. Results and discussion peaks, which shows that no Si-C(100.5 ev) or O-Si-C(101.8ev) bonds 20 exist in the surface layer of the KD-2 SiC fiber. The o1s 3. 1. Fiber surface characteristic analysis peak detected at 532.9ev in the survey XPS spectrum of KD-2 Sic SEM images ofKD- and Kp- 2 sic ibers ar represented in fig 2. tioe. hs presence of anweakx c is ne ak :at 2847ev indicates that a As shown in Fig 2a and b, the surface of KD-1 SiC fibers is rath small quantity of distributed on the Kd-2 SiC fiber. There- mooth, and no obvious defects are observed Compared with the fore, it can be confirmed that the silicon-based oxide is the main surface morphology of KD-1 SiCfibers, that of KD-2 SiCfibers(Fig 2c constituent of the surface layer of the KD-2 SiC fiber. 1O um Fig. 2. SEM images of KD-1(a and b)and KD-2(c and d)siC fibers.122 H. Liu et al. / Materials Science and Engineering A 525 (2009) 121–127 Table 1 Properties of KD SiC fibers. Type KD-1 KD-2 Diameter (m) 14–16 14–16 Number of filaments (fil/yarn) ∼1200 ∼1200 Tensile strength (MPa) 1800–2200 1500–1900 Density (g cm−3) −2.54 −2.55 C/Si atom 1.25 L23 Chemical compositions of fiber surface layer PyC Silicon-based oxide for transmission electron microscope (TEM) observation followed the preparation procedure described by Appiah et al. [18]. JEOL JEM-2010 and Philips CM 200 FEG equipped with a Gatan imag￾ing filter (GIF) system were used to characterize the interfacial microstructure and element distributions in the interphase region. X-ray photoelectron spectroscopy (XPS) analysis was done using a VG ESCA-LAB MK II apparatus with Al K radiation and calibrated against Au 4f7/2 and Cu 2p3/2 lines. Raman spectra were recorded with a Raman spectrometer HR 800 (Jobin-Yvon Company, France) in backscattering geometry at 532 nm excitation wavelength. The laser beam was focused in air at normal incidence on a small area of the fiber surface (ca. 1 m2), and the laser beam power was 1 mW. Raman spectra were recorded at wavenumbers from 800 to 2000 cm−1, and the acquisition time was 30 s. The phases of KD-1 and KD-2 SiC fibers were characterized by X-ray diffraction (XRD) analysis using monochromatic Cu K radiation with a D8 ADVANCE diffractometer (Bruker, Germany). 3. Results and discussion 3.1. Fiber surface characteristic analysis SEM images of KD-1 and KD-2 SiC fibers are represented in Fig. 2. As shown in Fig. 2a and b, the surface of KD-1 SiC fibers is rather smooth, and no obvious defects are observed. Compared with the surface morphology of KD-1 SiC fibers, that of KD-2 SiC fibers (Fig. 2c Fig. 1. Preparation route of the 2D-SiCf/SiC composites. and d) is relatively rough, and some strumae-like structure defects are found. These defects reduce the tensile strength of SiC fibers [19], such that the tensile strength of KD-2 SiC fibers is about 85% that of KD-1 SiC fibers. Survey XPS spectra recorded from the surface of KD-1 and KD-2 SiC fibers are shown in Fig. 3a. In the spectrum of KD-1 SiC fibers, no Si lines are observed. A single C 1s peak at 284.5 eV is detected, which is attributed to the C-C bond in the PyC. In addition, the pres￾ence of a weak O1s peak at 532.5 eV indicates that some oxygen exists on the KD-1 SiC fiber, which originate from a contamination by the glue or sample holder. So, it can be concluded that the PyC is the main constituent of the surface layer of the KD-1 SiC fiber. Con￾cerning KD-2 SiC fibers, the Si 2p and Si 2s peaks are all detected. In the Si 2p spectrum of KD-2 SiC fibers (Fig. 3b), only a single Si 2p peak at 103.6 eV is detected, which is assigned to the Si–O bond in silicon-based oxide, and the Si 2p peak cannot be fitted into sub peaks, which shows that no Si–C (100.5 eV) or O–Si–C (101.8 eV) bonds [20] exist in the surface layer of the KD-2 SiC fiber. The O1s peak detected at 532.9 eV in the survey XPS spectrum of KD-2 SiC fibers is attributed to the O–Si bond in silicon-based oxide. In addi￾tion, the presence of a weak C1s peak at 284.7 eV indicates that a small quantity of carbon is distributed on the KD-2 SiC fiber. There￾fore, it can be confirmed that the silicon-based oxide is the main constituent of the surface layer of the KD-2 SiC fiber. Fig. 2. SEM images of KD-1 (a and b) and KD-2 (c and d) SiC fibers.